In many female mammals, vaginocervical stimulation (VCS) received during mating modifies sexual responsiveness and initiates or induces several neuroendocrine changes which influence reproductive success. VCS is required in rodent for initiation of the endocrine changes of early pregnancy or pseudopregnancy (PSP), in particular twice-daily surges of prolactin (PRL) secretion which maintain corpus luteum function. The particular characteristics of the VCS received by the female during mating are critical determinants of whether PSP will occur, and there is a unique correspondence between the pattern of VCS which the female requires for initiation of pregnancy and the patterning of copulatory stimulation received by the female during mating. Therefore, this model system offers an opportunity to examine at the cellular level how the expression of behavior can influence neural function over a prolonged period. Despite advances in our understanding of the endocrine mechanisms responsible for PSP, our knowledge remains incomplete, particularly in the area of the initiation phase of the PRL surges. Recent work from the PI's laboratory has shown that a productive approach to the question of how mating stimulation initiates PRL surges is to use naturally-occurring patterns of coital stimulation to evaluate changes in neural function which are specific to PSP. Research carried out during the tenure of this grant will explore the proximal neural and endocrine changes which occur in response to VCS in several areas of the brain which the investigator's have identified to be involved in the process by which VCS is transduced into the PRL surge of early pregnancy/PSP. Experiments will: 1) determine which specific PRL responses to mating are responsible for PSP; 2) explore the role of the medial amygdala in transducing the afferent genitosensory input into the neuroendocrine changes of PSP; 3) examine whether ascending noradrenergic fibers are involved in initiating changes within the medial amygdala necessary for PSP; and 4) examine the role of oxytocin neurons in the paraventricular nucleus in the induction of PRL urges by mating. The broad research goal of this Independent Scientist Award application is to use neuroethological approaches to define the cellular mechanisms by which mating behavior initiates neuroendocrine responses of early pregnancy.